I know of no deposit account rule that would prohibit it. Just understand that, if the customer gets the loan and the free appraisal but decides a couple months after the mortgage closing to terminate the auto payment or maybe close the account, you won't have any recourse against the customer. Suing to recover the cost of the appraisal is likely to cost more than it's worth.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8